High-speed commutation device for heavy power applications

ABSTRACT

A high-speed commutation device using the effect of the fall of resistivity in pressure responsive materials under the action of very high pressures. Pressure is obtained in the form of a pressure wave generated by the detonation of an explosive excited by an electric detonator. The core of insulating material is located between two electrodes under the explosive charge and the transit of the shock wave causes a heavy fall of resistivity which establishes a contact of low residual resistance between the two electrodes. The invention is applied to the construction of starting switches and other similar devices and to switching methods.

United States Patent 1 1 Refouvelet et a1.

HIGH-SPEED COMMUTATION DEVICE FOR HEAVY POWER APPLICATIONS Inventors: Joseph-Paul-Marie Refouvelet, 65-

Tarbes; Joseph Jean Francois Pontico, 65-1-lautes-Pyrenees, both of France Foreign Application Priority Data Aug. 27, 1969 France ..6929291 US. Cl ..338/13 1111. C1. ..II0lc 7/00 Field OI Search ..338/13, 47, 2, 5;

References Cited UNITED STATES PATENTS 6/1970 Yamashita ..338/13 1 1 May 29, 1973 3,577,884 5/1971 Fujita .Q ..33s/2 ux 3,522,459 8/1970 Stubbs ..310/10 3,484,627 12/1969 Conger ....310/10 3,197,335 7/1965 Leszynski....-. "338/2 3,129,157 4/1964 Loeckenhoff ..310/10 Primary ExaminerR. Skudy Attorney-Waters, Roditi, Schwartz & Nissen 57 ABSTRACT A high-speed commutation device using the effect of the fall of resistivity in pressure responsive materials under the action of very high pressures. Pressure is obtained in the form of a pressure wave generated by the detonation of an explosive excited by an electric detonator. The core of insulating material is located between two electrodes under the explosive charge and the transit of the shock wave causes a heavy fall of resistivity which establishes a contact of low 'residual resistance between the two electrodes. The invention is applied to the construction of starting switches and other similar devices and to switching methods,

10 Claims, 5 Drawing Figures Mu ta ELECTRODE f ELECTRODE DIRECT/0N 0F SHOCK HUN-4, L 1 A'V/Ai B ELECTRODE [ELECTRODE D/RECT/O V 0F SHOCK HHH lV/A 32 ELECTRODE PATENTEDMAYZQ I975 3, 736, S45

sum 2 OF 2 HIGH-SPEED COMMUTATION DEVICE FOR HEAVY POWER APPLICATIONS BACKGROUNDv SUMMARY OF INVENTION An object of the present invention is to provide for the commutation and switching of large currents, for example, of the order of megamperes A) with short commutation periods of, for example, lower than 200 nanoseconds (2.10" sec.).

The application of very high pressures of the order of a 100 kilobars or more changes the crystal structure of insulating or semi-conductor materials and, among other properties, their electric conductivity.

In this way, decreases of resistivity of six to seven orders of magnitude or more can be obtained.

Further, the use of shock waves generated by explosives allows pressures of 100 to 500 kilobars to be obtained in extremely short periods of, for example, lower than 100 ns (10 sec.). I

Another object-of the present invention is the provision of an improved commutator founded on the aforesaid properties.

One aspect of the invention consists of using a shock wave generated by detonation of an explosive to induce pressures of the order of several hundred kilobars in an initially insulating material, the effect of such pressures being a very considerable decrease in the resistivity of the material.

The shock wave, produced by detonation of a small amount of explosive, can strike the material directly on issuing from the explosive or after passing into a metal anvil which can serve as a contact electrode or by reflection from a plate or anode. This last system permits obtaining much higher pressures of, for example, up to more than a megabar (10 bars).

The insulating material located between the two electrodes of the contact can, by way of nonrestrictive example, be I a mineral semi-conductor, either a single element or an intrinsic or doped compound (such as S, Se, Si, Te, GaP, GaS, etc.)

a thin metal semi-metallic or metal oxide coating;

an organic semi-conductor;

a'PN junction (plain diodes, Zener diodes, Tunnel diodes); or

an organic polymer deposited in a thin coating on the electrodes.

These materials are obtainable in the form of oriented monocrystals, such as polycrystals, compressed powders or thin coatings.

BRIEF DESCRIPTION OF DRAWING FIGS. 1 and 2 show diagrammatically principles of the device FIG. 1 showingconduction in direction of the shock and FIG. 2 showing conduction'in a direction at right angles to the shock direction;

FIG. 3 is a sectional view of a commutator provided in accordance with one of the embodiments of the invention; and 7 FIGS. 4 and 5 are respectively longitudinal and trans- I verse sections of a contact cell employed in accordance with the invention.

DETAILED DESCRIPTION The device of the invention (see FIGS. 3-5) consists of three principal parts 2 a fixed frame l6,a contact cell 17 and a pyrotechnic box 18.

The fixed frame 16 comprises base 1 with a detachable anvil 2 and the body 3 carrying contact cell 17 with'the pyrotechnic box 18.

Contact cell 17 is formed by two electrodes 12 separated from each other by insulating core 13 and between which current is to be passed upon explosion. This cell 17 is coated in a molded insulator 14 which is practically insensitive to pressure. Said cell can be easily changed after each firing.

Pyrotechnic box 18 includes a body 4 which is screwed onto body 3 of the fixed frame 16 and carries the pyrotechnic device 9 with detonator 10 and explosive charge 11. Body 4 also carries centering collar 7 and shield ring 8. The cover 5 carries the co-axial plug 15 connected to the firing arrangement. Gasket 6 guarantees the impermeability of the box which can be very easily replaced after each firing for recharging under prescribed safety conditions. I

The different variants of this commutator include transmission of the shock wave direct or through an anvil or plate reflection accelerated by explosive detonation.

The variants include the insulating materials subjected to pressure. Without limit the scope of the invention, the following materials can may be used: mineral and organic semi-conductors, PN junctions, insulators, thin coatings of metal, semi-metals, metal oxides and organic polymers. Another variant is the fitting of the commutator, which can be altered to enhance electrical reliability (firability), resistance to shock, simplicity of making it operative, and the performance efficiencies of the apparatus.

Example performance data for the apparatus or switching or commutation method are given hereunder by way of example a. Commutation period lower than 200 ns (2.10

sec.);

b. Conduction period from a few microseconds to several tens of microseconds;

c. Pre-closing resistance from a few ohms to several million ohms:

d. Residual resistance after closing, less than 10" O and ability to go down to less than 10 (I;

e. Allowable current up to l megampere (l0 A) and more, and ongoing energies of several megajoules (l0 joules). The said commutator can be used in all branches of impulse electrical engineering pertaining to heavy current and high powers, especially where there are requirements for highspeed commutation.

Referring to FIGS. 1 and 2, it is seen that electrodes 12 may, for example, include spaced and parallel ends 30 and 31 between which insulating core 13 is positioned or spaced, coplanar ends 32 and 33 between which core 13 is positioned.

What is claimed is:

l. A commutator comprising two electrodes and, between said electrodes, insulating means including insulating material which becomes a conductor when subjected to critical pressure; and explosive means in operative association with said insulating means for selective operation of the latter.

2. A commutator as claimed in claim 1 comprising anvil means, said insulating means being sandwiched between said anvil means and explosive means.

' 3. A commutator as claimed in claim 1 comprising an insulator covering said electrodes and insulating means and forming a detachable, replaceable cell therewith.

4. A commutator as claimed in claim 1 wherein said electrodes are spaced and parallel and include overlapping ends between which said insulating means is positioned.

5. A commutator as claimed in claim 1 wherein said electrodes are coplanar and include spaced ends between which said insulating means is positioned.

6. A commutator as claimed in claim 1 wherein said insulating means is of a material having relatively high initial resistance and adapted to charge to pass electric currents in the order of one megampere within a period of less than a microsecond.

7. A commutator as claimed in claim 1 comprising a frame detachably supporting said electrodes, insulating means and explosive means, and ignition means on said frame for selectively igniting said explosive means.

8. A commutator as claimed in claim 1 wherein said insulating means is selected from the groiip consisting of mineral semi-conductor, a metal coating, a semimetallic coating, a metal oxide coating, an organic semi-conductor, a PN junction, and an organic polymer.

9. A switching method comprising placing between two electrodes an insulator which responds to pressure by becoming a conductor, and selectively detonating an explosive adjacent the insulator to enable current to flow between the electrodes.

10. A commutator comprising two electrodes and, between said electrodes, insulating means which becomes and remains a conductor upon being subjected to a critical pressure. 

1. A commutator comprising two electrodes and, between said electrodes, insulating means including insulating material which becomes a conductor when subjected to critical pressure; and explosive means in operative association with said insulating means for selective operation of the latter.
 2. A commutator as claimed in claim 1 comprising anvil means, said insulating means being sandwiched between said anvil means and explosive means.
 3. A commutator as claimed in claim 1 comprising aN insulator covering said electrodes and insulating means and forming a detachable, replaceable cell therewith.
 4. A commutator as claimed in claim 1 wherein said electrodes are spaced and parallel and include overlapping ends between which said insulating means is positioned.
 5. A commutator as claimed in claim 1 wherein said electrodes are coplanar and include spaced ends between which said insulating means is positioned.
 6. A commutator as claimed in claim 1 wherein said insulating means is of a material having relatively high initial resistance and adapted to charge to pass electric currents in the order of one megampere within a period of less than a microsecond.
 7. A commutator as claimed in claim 1 comprising a frame detachably supporting said electrodes, insulating means and explosive means, and ignition means on said frame for selectively igniting said explosive means.
 8. A commutator as claimed in claim 1 wherein said insulating means is selected from the group consisting of mineral semi-conductor, a metal coating, a semi-metallic coating, a metal oxide coating, an organic semi-conductor, a PN junction, and an organic polymer.
 9. A switching method comprising placing between two electrodes an insulator which responds to pressure by becoming a conductor, and selectively detonating an explosive adjacent the insulator to enable current to flow between the electrodes.
 10. A commutator comprising two electrodes and, between said electrodes, insulating means which becomes and remains a conductor upon being subjected to a critical pressure. 